This invention relates to an improved electrostatic reproduction machine, but more particularly to an electrostatic reproduction machine having an improved toner dispensing apparatus.
In the practice of xerography as described in U.S. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic plate is electrostatically charged uniformly over its surface, and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern or latent electrostatic image in conformity with the configuration of the original pattern.
The latent electrostatic image is developed by contacting it with a finely divided electrostatically attractable material, such as a resinous powder. The powder is held in the image areas by the electrostatic fields on the layer. Where the field is greatest, the greatest amount of material is deposited, and where the field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the image of the original being produced. The powder image is subsequently transferred to a sheet of paper or other transfer member, and suitably affixed thereto to form a permanent copy.
The latest concept for electrostatic reproduction machines utilizes high speed flash exposure of a document, and a moving photoconductive material in the form of an endless belt which is continuously charged. Additionally, such reproduction machines are provided with a developing system which supplies toner particles in relatively large quantities for solid area coverage, such as a magnetic brush developing apparatus. Thus, after the belt passes the magnetic brush assembly for example, a xerographic powder image is formed on the belt which corresponds to the electrostatic latent image. This powder image is then transferred to a support surface (e.g., a sheet of paper) to which it is fused by a fusing assembly whereby the powder image is caused to adhere to the support surface permanently.
In electrostatic reproduction machines a latent electrostatic image is first produced on a photoreceptor. This latent image is then developed with a fine powder (toner) to produce a developed powder image which is subsequently transferred to a support surface such as paper. As used in most automatic xerographic reproduction machines, the fine toner particles are brought into rubbing contact with a triboelectrically remote and relatively coarser carrier material. The rubbing or mixing action causes the toner particles to become triboelectrically charged to a polarity opposite to that of the carrier, and opposite to that of the latent electrostatic image. This carrier/toner mixture is contained within a developer. In order to sustain continuous operation in an automatic electrostatic reproduction machine, the toner consumed in the development process must be periodically replaced within the developer. New toner has heretofore been packaged in a supply bottle or container, and the toner is poured directly from the container into a receptacle from which the toner will be dispensed. This pouring process has proved to be wasteful and contaminating because some airborn toner particles migrate away from the intended receptacle and onto surrounding machine parts and/or the operator's clothing.
It is often necessary, e.g., in certain color reproduction machines, to locate the toner supply at a location which is remote from the main developer. Also, in these machines, the size of the toner dispenser or toner supply is governed by the available space within the inside of the machine, which space is often at a premium.
Many toner dispensers utilize dispensing rollers to periodically dispense toner into the developer. Often, in these dispensers, the dispensing will begin without any problem but then stop because the toner has bridged or caked within the dispenser and the roller or other dispensing means is not in contact with the toner.
Consequently, what is needed is an improved toner dispensing apparatus having a cartridge which can be easily inserted into a machine and removed therefrom without the risk of contamination. This apparatus should be of relatively simple construction, and when necessary, it should be capable of being mounted at a location which is remote from the main developer. The apparatus should also prevent toner from caking or bridging within the apparatus.